Captions Api

Overview

Generate captions from a video's audio using Vosk speech recognition and burn them onto the video with custom styling.

Returns both the captioned video file and an SRT subtitle file.

The pipeline: download → extract audio → transcribe → generate subtitles → burn onto video.

positions : "bottom", "top", "center"

Endpoint

POST https://eranol.com/api/v1/ffmpeg/video/caption

Request Body

{
  "url": "https://cdn.example.com/video.mp4",
  "language": "en",
  "position": "bottom",
  "font_size": 24,
  "font_color": "white",
  "padding_top": 30,
  "outline_color": "black",
  "outline_width": 2,
  "padding_bottom": 30,
  "max_words_per_line": 7,
  "max_segment_duration": 3
}

Response Example

{
  "job_id": "f595b9ad-1e15-4452-b7c2-8f8ff09c0a34",
  "status": "pending",
  "message": "Job created. Poll status_url for progress.",
  "job_type": "caption",
  "result_url": "https://eranol.com/api/v1/ffmpeg/result/f595b9ad-1e15-4452-b7c2-8f8ff09c0a34",
  "status_url": "https://eranol.com/api/v1/ffmpeg/status/f595b9ad-1e15-4452-b7c2-8f8ff09c0a34"
}

Supported Languages

Pass any code below as the language parameter. Omit it entirely to let the API auto-detect the language.

Code	Language
en	English
zh	Chinese
es	Spanish
hi	Hindi
ar	Arabic
fr	French
pt	Portuguese
ru	Russian
de	German
ja	Japanese
ko	Korean
it	Italian
tr	Turkish
pl	Polish
nl	Dutch
vi	Vietnamese
id	Indonesian
th	Thai
ms	Malay
uk	Ukrainian
bn	Bengali
ur	Urdu
fa	Persian
sv	Swedish
ro	Romanian
cs	Czech
el	Greek
hu	Hungarian
da	Danish
fi	Finnish
no	Norwegian
sk	Slovak
he	Hebrew
bg	Bulgarian
hr	Croatian
sr	Serbian
ta	Tamil
te	Telugu
ml	Malayalam
kn	Kannada
gu	Gujarati
mr	Marathi
pa	Punjabi
af	Afrikaans
am	Amharic
as	Assamese
az	Azerbaijani
ba	Bashkir
be	Belarusian
bo	Tibetan
br	Breton
bs	Bosnian
ca	Catalan
cy	Welsh
et	Estonian
eu	Basque
fo	Faroese
gl	Galician
ha	Hausa
haw	Hawaiian
ht	Haitian Creole
hy	Armenian
is	Icelandic
jw	Javanese
ka	Georgian
kk	Kazakh
km	Khmer
la	Latin
lb	Luxembourgish
ln	Lingala
lo	Lao
lt	Lithuanian
lv	Latvian
mg	Malagasy
mi	Maori
mk	Macedonian
mn	Mongolian
mt	Maltese
my	Burmese
ne	Nepali
nn	Nynorsk
oc	Occitan
ps	Pashto
sa	Sanskrit
sd	Sindhi
si	Sinhala
sl	Slovenian
sn	Shona
so	Somali
sq	Albanian
su	Sundanese
sw	Swahili
tg	Tajik
tk	Turkmen
tl	Tagalog
tt	Tatar
uz	Uzbek
yi	Yiddish
yo	Yoruba

Use Cases

1. English captions (default)

Request Body

{
  "url": "https://cdn.example.com/video.mp4",
  "language": "en",
  "position": "bottom",
  "font_size": 24,
  "font_color": "white",
  "padding_top": 30,
  "outline_color": "black",
  "outline_width": 2,
  "padding_bottom": 30,
  "max_words_per_line": 7,
  "max_segment_duration": 3
}

2. Auto-detect language

Request Body

{
  "url": "https://cdn.example.com/video.mp4",
  "position": "bottom",
  "font_size": 24,
  "font_color": "white",
  "padding_top": 30,
  "outline_color": "black",
  "outline_width": 2,
  "padding_bottom": 30,
  "max_words_per_line": 7,
  "max_segment_duration": 3
}

3. Spanish, top position

Request Body

{
  "url": "https://cdn.example.com/video.mp4",
  "language": "es",
  "position": "top",
  "font_size": 28,
  "font_color": "yellow",
  "padding_top": 40,
  "outline_color": "black",
  "outline_width": 2,
  "padding_bottom": 30,
  "max_words_per_line": 6,
  "max_segment_duration": 3
}

Error Codes

Code	Meaning
401	Missing or invalid API key
402	Insufficient credits
422	Validation error — check your request body
429	Rate limit exceeded — slow down requests
500	Internal server error — try again or contact support